org.springframework.beans.factory
Interface SmartFactoryBean<T>

Extension of the FactoryBean interface. Implementations may
indicate whether they always return independent instances, for the
case where their FactoryBean.isSingleton() implementation returning
false does not clearly indicate independent instances.

Plain FactoryBean implementations which do not implement
this extended interface are simply assumed to always return independent
instances if their FactoryBean.isSingleton() implementation returns
false; the exposed object is only accessed on demand.

NOTE: This interface is a special purpose interface, mainly for
internal use within the framework and within collaborating frameworks.
In general, application-provided FactoryBeans should simply implement
the plain FactoryBean interface. New methods might be added
to this extended interface even in point releases.

isPrototype

Is the object managed by this factory a prototype? That is,
will FactoryBean.getObject() always return an independent instance?

The prototype status of the FactoryBean itself will generally
be provided by the owning BeanFactory; usually, it has to be
defined as singleton there.

This method is supposed to strictly check for independent instances;
it should not return true for scoped objects or other
kinds of non-singleton, non-independent objects. For this reason,
this is not simply the inverted form of FactoryBean.isSingleton().

isEagerInit

boolean isEagerInit()

Does this FactoryBean expect eager initialization, that is,
eagerly initialize itself as well as expect eager initialization
of its singleton object (if any)?

A standard FactoryBean is not expected to initialize eagerly:
Its FactoryBean.getObject() will only be called for actual access, even
in case of a singleton object. Returning true from this
method suggests that FactoryBean.getObject() should be called eagerly,
also applying post-processors eagerly. This may make sense in case
of a singleton object, in particular if
post-processors expect to be applied on startup.